Piezoelectric-fluid electromechanical transducer

ABSTRACT

The transducer has a fluid chamber mounting a piezoelectric element at one end and a piston slidably mounted in a reduced diameter portion of the chamber opposite the element. A timebase, including a high frequency oscillator and a frequency divider, applies an electrical signal across the piezoelectric element whereby the element moves to displace the fluid in the chamber thereby driving the piston outwardly against the bias of a spring. The piston is coupled to the gear train of a timepiece. The timed electrical signal is thus converted to an incremental mechanical movement which is amplified by the fluid system to provide timed indexing of the gear train.

United States Patent 1 21 Inventor Richard S. Walton Lancaster, Pa. [21 I Appl. No 855,793 22] Filed July 23, 1969 Division of Ser. No. 724,144, Apr. 25. 1968. Pat. No. 3,509,714 [45] Patented July 27, 1971 [73] Assignee Hamilton Watch Company Lancaster, Pa.

Original application Apr. 25, 1968, Ser. No. 724,144, now Patent No. 3,509,714. Divided and this application July 23, 1969, Ser. No. 855,793

[54] PlEZOELECTRlC-FLUID ELECTROMECHANICAL Primary Examiner-Milton O. l-lirshfield Assistant Examiner-B. A. Reynolds AttorneyLe Blanc & Shur ABSTRACT:'The transducer has a fluid chamber mounting a piezoelectric element at one end and a piston slidably mounted in a reduced diameter portion of the chamber opposite the element. A timebase, including a high frequency oscillator and a frequency divider, applies an electrical signal across the piezoelectric element whereby the element moves to displace the fluid in the chamber thereby driving the piston outwardly against the bias of a spring. The piston is coupled to the gear train of a timepiece. The timed electrical signal is thus converted to an incremental mechanical movement which is amplified by the fluid system to provide timed indexing of the gear train.

PATENTEU JUL27 ISII FIGI INVENTOR FLUID AMPLIFIER GEAR TRAIN ELECTROMECHANICIIL ACTIVE ELEMENT DIVIDER NETWORK IIMEBASE RICHARD s WALTON ATTORNEYS PIEZOELECTRlC-FLUID ELECTROMECIIANICAL TRANSDUCER This application is a division of copending application Ser. No. 724,144, filed Apr. 25, 1968, now U.S. Pat. No. 3 ,509,7 14.

The present invention relates to an electromechanical timepiece and particularly to a timepiece having an electricalmechanical transducer including an electromechanically active element wherein the motion of the element under an applied electrical signal having a predetermined frequency is amplified through a fluid system to drive the gear train of a timepiece.

With the employment of periodic signal sources, such as crystal controlled oscillators or free-running multivibrators or the like, as high frequency timebases, it has been found desirable to provide direct electrical to mechanical energy conversions or transducers whereby the mechanical parts of the timepiece would be driven directly from the transducer. Complex electrical circuitry has heretofore been provided to perform this conversion. However, cost, power, and space limitations in timepieces, particularly watches, have effectively precluded use of such circuitry.

In direct electrical to mechanical conversions employing elements fonned of electromechanically active material, including piezoelectric elements, the mechanical motion or distortion characteristic of the material when an electrical signal is applied across the elements is extremely small. Various attempts to amplify this mechanical motion have been tried. One such attempt employs stacked piezoelectric elements connected'to a lever arrangement whereby the motion of the elements in response to an applied voltage across each element is amplified through the stack and lever arrangement.

In this and other attempts, space and friction limitations have proven difficult to overcome and a usable magnitude of mechanical motion hasbeen difficult to obtain.

' The present timepiece employs an electromechanical transducer having an element formed of electromechanically active material which element moves or is distorted in a predetermined direction in response to an impressed electrical signal.

The electrical signal is provided by a high frequency timebase,

the output frequency of which is reduced through a frequency divider and impressed on the electromechanically active element. This element forms a wall portion of a fluid chamber which also has a reduced diameter area or restriction. A piston is slidably received in this reduced area and is biased inwardly into the fluid chamber by a spring. A tooth on the piston is disposed to engage the teeth on a ratchet wheel which is geared to the gear train of the timepiece. The element distorts or moves inwardly into the fluid filled chamber in response to an electrical signal impressed thereacross to drive the piston member outwardly against the bias of its spring, thereby driving the gear train. Due to the relative areas of the element and piston member which confront the fluid in the chamber, the incremental motion or distortion of the element is amplified to provide a piston displacement usable in and sufficient to drive the gear train of a timepiece.

Accordingly, it is a primary object of the present invention to provide an improved electrical-mechanical transducer having direct mechanical motion amplification.

It is another object of the present invention to provide an improved timepiece of the type employing an electricalmechanical transducer.

It is still another object of the present invention to provide an improved timepiece having an electrical-mechanical transducer of the type employing electromechanically active material providing mechanical motion in response to an applied voltage.

It is a further object of the present invention to provide an improved timepiece which is simple in construction and has a minumum number of moving parts.

These and further objects and advantages of the present invention will become more apparent upon reference to the following specification, claims and appended drawings wherein:

FIG. I is a block diagram illustrating the power train of a timepiece constructed in accordance with the present invention;

FIG. 2 is a schematic illustration of an electrical-mechanical transducer and fluid amplifier employed in the timepiece hereof;

FIG. 3 is an enlarged schematic illustration of the fluid amplifier and another type of electrical-mechanical transducer;

FIG. 4 is a horizontal cross-sectional view thereof taken about on line 44 of FIG. 3.

Referring now to the drawings and particularly to FIG. 1, there is schematically illustrated a timepiece comprising a high accuracy timebase 10, the output frequency of which is divided by a divider network 12 to provide a frequency in a range useful to drive the gear train of a timepiece. Timebase 10 may comprise any suitable periodic signal source, for example, a crystal controlled oscillator, a free-running or a stable multivibrator, or any other type of periodic source suitable for timekeeping purposes.

Generally, the electrical signal from timebase 10 and divider network 12 is applied to a transducer 14 across an element thereof, formed of an electromechanically active material having the property of providing a physical distortion or movement when a potential gradient is applied across its major surfaces. Upon removal of the electrical signal, the element returns to its original shape. Elements having this type of mechanical action in response to an applied electrical signal are well known in the art and are most often piezoelectric elements, but may be magnetostrictive or electrostrictive elements as desired. As further seen in FIG. 1, the slight or incremental mechanical motion of the electromechanically active element 14 caused by the imposition of the electrical signal is amplified through a fluid system 16 to drive the gear train 18 of a timepiece.

Referring now to FIG. 2, there is shown an element 20, preferably formed of electromechanically active material having the above-noted characteristics and disposed in and at the lower end of a generally cylindrical container or chamber 22 containing a fluid 24. A base cap 26 is suitably secured to the sidewalls of container 22 in underlying relation to element 20. One type of electromechanically active element 20 comprises a conventional piezoelectric element which may be formed of crystalline quartz, Rochelle Salt, ammonium dihydrogen phosphate, or the like, and which is provided electrically conductive coatings 28 and 30 on opposite surfaces thereof. The lower surface of element 20 is preferably fixed to cap 26 whereby element 20 is free for axial inward movement or distortion. Electrical wires 32 and 34 connect with conductive plates 28 and 30 on opposite sides of element 20 for applying the electrical signal from timebase l0 and frequency divider 12 across element 20. Wire 32 extends upwardly within and is insulated from the sidewall of container 22 for connection with upper coating 28 while wire 34 may extend directly through cap 26 for connection with lower coating 30. Alternatively, element 20 could be secured to the walls of container 22 about its periphery whereby element 20 would be free for axial movement in both directions.

The opposite end of chamber 22 has a reduced diameter portion 36 which slidably receives one end of a piston member 38. A spring 40 connects to the opposite end of piston member 38 biasing member 38 inwardly into container 22 such that the lower end of member 38 is maintained in confronting relation with the fluid 24 in container 22. A tooth 42 is formed on the side of piston member 38 for engagement with a ratchet wheel 44, having teeth 45. The teeth 45 on ratchet wheel 44 are preferably formed of ferromagnetic material and a magnet 46 is positioned in opposed relation to one of the teeth 45 to provide a restraining force to wheel 44. The gear train of a timepiece is schematically illustrated at 48 and is suitably geared to wheel 44. It will be seen that axial reciprocation of piston member 38 steps ratchet wheel 44 unidirectionally to drive gear train 48. Magnet 46 acts on the ratchet wheel teeth 45 as they are successively positioned in opposed relation thereto to restrain index wheel 44 from power train for the presentreverse rotation when tooth 42 clicks back to the normal illustrated position. This type of magnet-tooth cooperation is described in U.S. Pat. No. 3,158,988 of common assignee herewith.

In use, the electrical signal from the timebase l and frequency divider l2 is periodically applied across electromechanically active element 20 via wires 32 and 34 and conductive surfaces 28 and 30. With each electrical pulse, element 20 characteristically moves or distorts in an axial direction and, with cap 26 preventing axial movement of element 20 in a downward direction as seen in FIG. 2, element 20 moves axially into container 22 exerting a force through fluid 24 against member 38. Piston member 38 is thus displaced outwardly against the bias of spring 40 and a tooth 42 steps ratchet wheel 44 (such that the next tooth 45 is positioned in opposed relation to magnet 46), thereby driving gear train 48. Upon removing the applied electrical signal, element 20 returns to its normal configuration whereby spring 40 urges piston member 38 inwardly into container 22 to locate tooth 42 behind the next tooth 45 on ratchet wheel 44 with magnet 46 restraining index wheel 44 from reverse rotation as tooth 42 clicks past the next tooth. This operation is repeated and it will be seen that the reciprocating motion of piston member 38 follows the periodic movement of element 20 and the frequency of the applied signal to drive ratchet wheel 44 and gear train 48 unidirectionally.

Referring now to FIGS. 3 and 4, there is shown a cylindrical chamber 220, similar to the chamber 22 in the previous embodiment, the lower end of a piston member 38a being slidably received in a reduced diameter portion 360 of a container 22a containing fluid 24a. A piston or disc 50 is slidably received through the lower open end of container 22a. in this form, the electromechanical active element 14 is of the Bimorph type and comprises a pair of layers 52 of piezoelectric ceramic material separated by a metallic spacer 54 which may be formed of brass. Conductive electrode layers 56 and 58 are attached in any suitable manner to the outer surfaces of the piezoelectric layers 52. This electromechanically active Bimorph element has an annular configuration with a central aperture. A pin 60, secured to the disc 50, is suitably fastened to the Bimorph" element within its aperture. The annular Bimorph" element is rigidly secured about its periphery to the lower end of container 22a and a pair of electrical wires 32a and 34a connect with electrode layers 56 and 58 respectively for applying the periodic electrical signal from timebase l0 and frequency divider 12.

In use, the periodic application of the electrical signal fro timebase across the Bimorph" element characteristically moves or distorts the annular element in an axial direction toward and away from fluid chamber 220. This mechanical distortion or movement reciprocates piston 50 within chamber 22a exerting a force through the fluid 240 against member 38a. The action of piston member 380 is similar in this form to the action of piston member 38 in the previous form and accordingly the periodic movement of the Bimorph element is followed by reciprocating motion of piston member 38a to drive ratchet wheel 44 and gear train 48 unidirectionally. It will be appreciated that Bimorph" element 14 could act directly against the fluid 24a without the intermediary of piston 50 if desired.

It is a feature of the present invention that the slight or incremental mechanical movement of the electromechanical active element 14 in each fonn hereof in response to the imposition of an electrical signal is amplified through the fluid system to displace the associated piston member 38, 38a a distance sufficient to provide useful work, i.e., sufficient to step the gear train of a timepiece. To this end, the area of piston member 38, 380 which confronts fluid 24, 24a in container 22, 22a is preferably considerably smaller than the respective areas of element 20 and piston 50 which confront the fluid. The displacement of piston member 38, 38a, being proportional to the ratio of the areas of the element 20 and piston member 38, or piston 50 and member 38a, as the case may be, which confront the fluid, 18 thus amplified to the extent that the displacement is sufficient to step wheel 44 and hence drive gear train 48.

It is thus seen that the objects of the invention are fully accomplished in that there is provided a simple and improved electrical-mechanical transducer for a timepiece of the type utilizing an electromechanically active material. Moreover,

' the slight or incremental mechanical movement of the electromechanically active element is uniquely amplified through the fluid system hereof to provide a mechanical movement or displacement sufficient to step an index wheel and thereby drive the gear train of a timepiece.

The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiment is therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

What I claim and desire to be secured by U.S. Letters Patent 1. An electromechanical transducer comprising a fluid container, a relatively smaller piston closing off one portion of said container, a relatively larger piston closing off a second portion of said container and adapted to communicate in force transfer relation with said smaller piston through the fluid in said container, an annular piezoelectric bimorph spaced from said larger piston and having its outer edge fixed to a support, means for coupling an electrical signal to said bimorph, and means connecting said larger piston to the center of said bimorph.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,596 ll6 Dated Jul 27, 1971 Inventor(s) RICHARD S. WALTON It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In Column 1, line 72 "minumum" should read -minimum- In Column 2 line 36, "preferably formed" should read --preferably cylindrical, formed-.

Signed and sealed this 22nd day of February 1972.

( s EAL Attest:

EDWARD M.FLETCHEH, JR. ROBERT GOTTSCHALK Attesting Officer Commissionerof Patents )RM PO-TOSO (10-69) USCOMM-DC 60375-P09 

1. An electromechanical transducer comprising a fluid container, a relatively smaller piston closing off one portion of said container, a relatively larger piston closing off a second portion of said container and adapted to communicate in force transfer relation with said smaller piston through the fluid in said container, an annular piezoelectric bimorph spaced from said larger piston and having its outer edge fixed to a support, means for coupling an electrical signal to said bimorph, and means connecting said larger piston to the center of said bimorph. 